The Brazilian's previous deal had been due to expire on June 30, with the club announcing his extension on Wednesday as part of a wider update on its youth and feeder team structures.
Belletti, who joined Barcelona's youth coaching staff in 2023, will now begin a second consecutive season in charge of the club's reserve side.
The former defender took the reins at Barca Atletic last summer, having enjoyed a highly successful campaign with the Juvenil A side, where he won a domestic and continental treble of the Copa, Liga and UEFA Youth League.
In the 2025-26 season, Barca Atletic recorded 14 wins, 10 draws and 10 defeats across their 34 league matches in the Primera Federacion.
In his first year in charge of the club's second team, the 49-year-old met the objectives set for developing and promoting young players, with several of his squad going on to feature for Hansi Flick's first team during the campaign.
The Brazilian coach gave opportunities to numerous academy players throughout the season, with 21 different players making their Barca Atletic debuts, many of them still at youth level.
In total, 42 players featured for the side across the campaign as Belletti rotated his squad extensively, building valuable senior experience among the club's brightest young prospects.
Before returning to Barcelona, Belletti worked as an assistant coach with the first team at Cruzeiro, and held the position of Under-20 coach at Sao Paulo between September 2022 and June 2023.
His reappointment comes as Barcelona continues to invest heavily in its broader football structure beyond the first team, with the club keen to maintain continuity across its development pathway as several of Flick's squad members continue to emerge through the same system Belletti now oversees.
The extension ensures stability in a role that has become increasingly significant for Barcelona, given the number of recent first-team contributors who have progressed through Barca Atletic in the past two seasons.
Belletti's playing career at Barcelona, where he famously won the Champions League in 2006, has given him a level of credibility within the club's youth structure that few other coaches in the system can match.
His ability to blend results with player development has made him a trusted figure among the club's hierarchy, with Barcelona keen to ensure continuity at a level that increasingly feeds talent directly into Hansi Flick's senior squad.